An inflammation is one of the protective responses in the living organisms which aims at removal of foreign substances, pathogenic bacteria and so on, as well as repair of damaged tissues. When inflammatory stimulation is received, the microcirculatory system responds and particularly increases vascular permeability. The vascular permeability is promoted by chemical mediators and cytokines. Sequentially, chemotaxis, migration and activation of neutrophiles are induced, foreign substances and pathogenic bacteria are phagocytosed at the sites of inflammation, and chemical mediators are released to induce inflammatory responses. Subsequent to neutrophiles, chemotaxis and recruitment of macrophages at the local sites occur, and activated macrophages, like neutrophiles, phagocytose foreign substances, pathogenic bacteria, disintegrated tissues and so on to produce various cytokines. Then, pathogenic bacteria, foreign substances and damaged tissues are removed and the tissues are reconstructed, whereby the inflammation comes to an end. The above-mentioned process occurs in normal inflammatory responses. In allergy and autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus, however, abnormal immune responses prolong inflammation and cause strong systemic symptoms.
Many cytokines are involved in various processes of inflammatory responses. For example, IL-1, TNF-.alpha. and IL-8 are responsible for the chemotaxis, adhesion to vascular endothelial cells, and migration into vascular walls, of leukocytes, which are seen during migration of leukocytes into the sites of inflammation, wherein IL-1, TNF-.alpha. and IL-8 activate neutrophiles to cause release of lysosomal enzymes and production of active oxygen and prostaglandin, thus inducing inflammation. When IL-1, TNF-.alpha. and IL-6 migrate into the circulatory system, they act on liver to induce production of acute phase inflammatory protein (e.g., CRP and SAA), and act on bone marrow to increase neutrophiles and platelets. In inflammations of connective tissues, such as rheumatoid arthritis (RA), IL-1 and TNF-.alpha. are said to activate fibroblasts and osteoclastic cells and induce production of prostaglandin and collagenase [Mebio, 11 (2), 18-23, (1994)].
As stated in the foregoing, IL-1 and TNF-.alpha. play a central role in various aspects of inflammatory responses.
Meanwhile, IL-8 is produced not only by peripheral blood monocytes and tissue macrophages, but also by large granular lymphocytes (LGL) known as natural killer cells, T lymphocytes and various tissues and cells such as fibroblasts, vascular endothelial cells and epidermal keratinocytes. Examples of production stimulators include mitogen lectins such as LPS, PHA, PSK (Coriolus versicolor-derived protein-bound polysaccharide, Krestin) and cytokines such as IL-1 and TNF-.alpha..
Although most of these cells barely produce IL-8 constantly, upon stimulation with the above-mentioned IL-8 production stimulators, they produce more than 100 times greater amounts of IL-8 within 24 hours as compared to the production without stimulation. For example, when human peripheral blood monocytes are stimulated with PSK, IL-8 mRNA is induced within an hour, and production amount of IL-8 mRNA reaches its peak in 3 hours, and gradually decreases with time. Along with the induction of IL-8 mRNA, IL-8 protein having neutrophile chemotaxisis ability is detected in the medium at 3 hours after the stimulation and increases with time. IL-8 mRNA is induced in the same manner in time as in the stimulation of IL-1 and TNF-.alpha.. IL-8 is noticeably stable to protease produced by activated macrophage and the like.
The in vitro biological activities of IL-8 include chemotactic promotion, induction of degranulation, respiratory burst induction, lysosomal enzyme release induction, induction of adhesion to unstimulated or stimulated vascular endothelial cells, promotion of extravascular migration, reinforcement of expression of adhesion factors, leukotriene B.sub.4 -HETH release induction and the like with regard to neutrophiles; chemotactic promotion with regard to T cells; suppressive effect on IgE production by IL-4 with regard to B cells; and chemotactic promotion and histamine.multidot.leukotriene release induction with regard to basophils. IL-8 also has in vivo activities of induction of migration of neutrophiles and lymphocytes, induction of neutrophilia, reinforcement of vascular permeability, and neutrophile-dependent arthrosynovial destruction [Rinsho Men-eki, 25 (8), 1013-1020 (1993)].
As mentioned earlier, IL-8 has various effects on neutrophiles. It has been gradually clarified that IL-8 also acts on T lymphocytes, basophils, monocytes, keratinocytes and melanoma cells, besides neutrophiles. The biological activities and target cells thereof are found to be diverse like other cytokines.
It has been known that IL-8 realizes, in vivo, migration of neutrophiles and lymphocytes at the sites of subcutaneous injections, and increases homing of T lymphocytes to local lymph nodes. It has been also known that an intravenous or intraperitoneal injection of IL-8 markedly increases neutrophile counts in peripheral blood, and administration in large amounts thereof causes destruction of alveoli. In addition, an injection of IL-8 into rabbit intra-articular joint space is known to lead to arthrosynovial destruction with migration of large amounts of neutrophiles. These results suggest strong inflammation induction by IL-8 in vivo.
In view of the fact that IL-8 has various actions besides chemotactic stimulation of neutrophile, that IL-8 was detected in synovial fluid in patients with gout or rheumatic arthritis, that IL-8 was detected from skin pieces of patients with dermatitis such as psoriasis, that IL-8-like chemotactic factor is produced by peripheral blood monocytes in asthma, and that IL-8 was detected in peripheral blood of patients with sepsis which is considered to be one of the causes of adult respiratory distress syndrome (ARDS), it is evident that IL-8 is involved in various diseases such as inflammation.
Therefore, a substance capable of suppressing cytokines responsible for inflammations, such as IL-1, IL-6, IL-8 and TNF-.alpha., is extremely useful as a new type of medicine for noninfectious or infectious diseases accompanied by neutrophile migration, which are represented by rheumatic diseases (e.g., rheumatoid arthritis); arthritis due to gout; systemic lupus erythematosus; dermatopathy (e.g., psoriasis, pustulosis and atopic dermatitis); respiratory diseases (e.g., bronchial asthma, bronchitis, ARDS and diffused interstitial pneumonia); inflammatory bowel diseases (e.g., ulcerative colitis and Crohn's disease); acute or chronic hepatitis inclusive of fulminant hepatitis; acute or chronic glomerulonephritis; nephropyelitis; uveitis caused by Behoet disease and vogt-Koyanagi Harada disease; Mediterranean fever (polyserositis); ischemic diseases (e.g., myocardial infarction); and systemic circulatory failure and multi-organ failure caused by sepsis. In particular, such substance is expected to be effective as an anti-inflammatory agent based on new action mechanisms.
With such background of the art, compounds having inhibitory activity on inflammatory cytokines, such as IL-8, have been recently reported. For example, Japanese Patent Application under PCT laid-open under Kohyo No. 7-503017 discloses an imidazole derivative such as 4-(4-fluorophenyl)-2-(4-methylthiophenyl)-5-(4-pyridyl)imidazol as a cytokine inhibitor; Japanese Patent Application under PCT laid-open under Kohyo No. 7-503018 discloses pyridyl-substituted imidazole derivatives such as 1-(4-pyridyl)-2-(4-fluorophenyl)-4-phenylimidazol as cytokine inhibitors; and Japanese Patent Unexamined Publication No. 3-34959 discloses naphthalenemethaneamino derivatives having cytokine inhibitory activity. However, these publications do not suggest the compound of the present invention.
In addition, compounds having inhibitory activity on protease involved in inflammatory diseases have been reported. For example, Japanese Patent Unexamined Publication No. 4-330094 discloses t-butyl-oxycarbonyl-trimethylsilyl-Ala-Pro-NH-CH[(CH.sub.2).sub.3 N.sub.3 ]-B-pinandiole as a serine protease inhibitor of thrombin which induces pre-inflammatory changes of IL-1 and the like. Japanese Patent Examined Publication No. 7-53705 discloses phenylalanine derivatives such as N-(trans-4-amino-methylcyclohexylcarbonyl)-L-phenylalanine 4-acetylanilide. However, this publication relates to a compound characteristically having amino at one end of phenylalanine and 4-aminomethyl-6-membered ring-carbonyl group at the other end, which relates to a protease inhibitor, and does not relate to an inflammatory cytokine production suppressor, such as the compound of the present invention.
An object of the present invention is to provide a compound usable as a novel selective anti-inflammatory agent which suppresses production and release of inflammatory cytokines such as IL-8, IL-1, TNF-.alpha., IL-6, and the like.
In addition, an object of the present invention is to provide a pharmaceutical agent comprising said compound.